Direct conversion of CO2 to a jet fuel over CoFe alloy catalysts.

The direct conversion of carbon dioxide (CO2) using green hydrogen is a sustainable approach to jet fuel production. However, achieving a high level of performance remains a formidable challenge due to the inertness of CO2 and its low activity for subsequent C-C bond formation. In this study, we prepared a Na-modified CoFe alloy catalyst using layered double-hydroxide precursors that directly transforms CO2 to a jet fuel composed of C8-C16 jet-fuel-range hydrocarbons with very high selectivity. At a temperature of 240°C and pressure of 3 MPa, the catalyst achieves an unprecedentedly high C8-C16 selectivity of 63.5% with 10.2% CO2 conversion and a low combined selectivity of less than 22% toward undesired CO and CH4. Spectroscopic and computational studies show that the promotion of the coupling reaction between the carbon species and inhibition of the undesired CO2 methanation occur mainly due to the utilization of the CoFe alloy structure and addition of the Na promoter. This study provides a viable technique for the highly selective synthesis of eco-friendly and carbon-neutral jet fuel from CO2.

An In Situ Temperature-Dependent Study of La2O3 Reactivation Process.

Lanthanum-containing materials are widely used in oxidative catalytic and electrocatalytic reactions such as oxidative coupling of methane (OCM) and solid oxide fuel cells (SOFCs). However, many of these materials are highly susceptible to air contamination which means ex situ characterization results generally cannot be associated with their reactivity. In this study, the activation processes of an in situ-prepared bulk La2O2CO3 sample and an ex situ as-prepared La(OH)3 sample are in situ investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and online mass spectroscopy (MS). Results indicate that the La2O2CO3 sample, during linear heating to 800°C, always contains some carbonates near the surface region, which supports a two-step model of bulk carbonate decomposition through surface sites. The La(OH)3 sample structure evolution is more complex due to contaminations from air exposure. Together with TGA results, online mass analysis of water and CO2 signal loss showed that three major catalyst structure phase change steps and a preheating up to 800°C are required for the as-prepared material to be transferred to La2O3. This process is carefully investigated combining the three in situ methodologies. XPS and XRD data further reveal transformations of variety of in situ surface structures and forms including hybrid phases with hydroxyl, carbonates, and oxide as the sample heated to different temperatures within the range from 200 to 800°C. The results provide useful insights on the activation and deactivation of La-contained materials.

Correction: Understanding of binding energy calibration in XPS of lanthanum oxide by in situ treatment.

Correction for 'Understanding of binding energy calibration in XPS of lanthanum oxide by in situ treatment' by Jerry Pui Ho Li et al., Phys. Chem. Chem. Phys., 2019, 21, 22351-22358.

Understanding of binding energy calibration in XPS of lanthanum oxide by in situ treatment.

Rare earth oxides have seen increased usage over the years in batteries and catalysts. Due to their unique electronic properties, they are the subject of fundamental and practical interest. However, the complexity in their electronic structures makes unambiguous characterization, such as X-ray photoelectron spectroscopy (XPS), very challenging. Lanthanum oxide (La2O3) has attracted special attention as a promising catalyst for the oxidative coupling of methane (OCM) reaction. In this work, a new and reliable way of XPS calibration is developed by applying various in situ preparations for a nanorod La2O3 catalyst to intentionally form different lanthanum compounds, followed by XPS characterization and corroboration with first principles calculations. To form different compounds, five sample treatments were performed including heating in vacuum and treatment with O2, CH4, CO2, and H2O, which are all relevant to OCM reaction conditions. Adventitious carbon or lattice oxygen, as conventional calibration standard species for energy scale, is only suitable for one or few in situ prepared surfaces. Our results also clearly demonstrate the vital difference between performing the ex situ analysis after exposure of the sample to the atmosphere and the in situ analysis. By carefully comparing the spectra of various photoemission peaks of different compounds, we conclude that the binding energy of 102.2 eV for the La 4d7/2 peak can be used as the internal calibration standard for all considered samples. Furthermore, different oxygen species were unambiguously identified by matching the oxygen 1s binding energies from the in situ measurements and first principles predictions.